Oregon 400t + Heart Rate Monitor

Last year I bought Oregon Heart Rate Monitor (soft) and used with my Oregon 400t without any problem.
Now I tried it again, but Oregon does not find device. I changed batteries but did not help.
Is there possibility to check where the prob lies? Can I reset HRM somehow? I don't want to buy new HRM and problem lies at Oregon!
My location is Vienna/Austria - maybe someone has HRM to try with my Oregon (PM?).

I alway wet the belt / sensor pads before wearing and last time I had it on biking at average speed of 25 km/h for 45 minutes, so you can believe it was wet after!
But thank you anyway for you kind advices.

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